The most fascinating class of behavioral mutant in Drosophila is the bang- sensitive paralytic mutant (BS mutant). The class is large and encompasses mutants for at least 8 different loci. There are several extremely interesting features associated with the BS mutants. a) The mutants are completely paralyzed for about 2 min by a sharp mechanosensory stimulation. b) The bang-sensitivity is suppressed unconditionally by the temperature-sensitive paralytic mutations nap(ts) and para(ts) in double mutant combinations. c) There is a refractory period in newly awakened flies during which the mutant is immune to the paralyzing effects of mechanical stimulation. d) The BS mutants all have a temperature- sensitive paralytic phenotype. These features point to a common defect involving some fundamentally important feature of electrical excitability. At present, the best explanation for the BS mutant defect is that they have alterations in transmitter release. The study of BS mutants, at present, marks one of the only ways we have to approach the genetics and molecular biology of this fundamentally important problem in neurobiology. For this proposal, we focus on mutants at two loci: bangsenseless (bss) and easily shocked (eas) as models for the class. We have examined mutants electrophysiologically and shown that they exhibit a failure of synaptic transmission in response to high frequency stimulation. Molecular analysis and preliminary biochemistry has shown that the eas gene encodes a choline/ethanolamine kinase which acts in the synthetic pathway for producing the major insect phospholipids phosphatidyl choline and phosphatidyl ethanoloamine. On the basis of sequence similarity, the bss gene product appears to be a cyclophilin A which acts as a cyclosporin A binding protein and as a peptidylprolyl isomerase. We suspect that the gene products participate in synaptic vesicle processing during synthesis and recycling. In the proposed experiments, we will clarify the biochemical deficits of these mutants and determine normal expression patterns of these genes on the way to determining their role in synaptic transmission. We will also begin the analysis of other BS genes and also genes whose products interact with eas and bss. We are also proposing an electron microscope examination of mutant defects and will initiate a study of synaptic vesicle release in BS mutants using optical recording methods.